Can only be copied via Shroud of Reversal. As far as I've noticed, Blizzard reduced the number of abilities that can be Dark Simmed compared to Catacylsm, probably to just make it part of a DK's utility in PvP.

Protectors: Lightning Bolt, Maybe the Lightning Prison, but they are immune to it in any case.
Tsulong: Donut.
Lei Shi: "And we have a winner! What do we have for him, Johnny?" "It's didley squat! From the makers of jack squat, it's nothing, zero, zilch, nada, bupkus, nothing!"
Sha: Haven't checked the adds, but nothing from Shaington himself.

Call to arms, the trumpets sound
Hand puppets storm the base, flags up now cannons rage
All clowns head for the rear, slingshots fire to the air
Toy horses start the charge, Robot chessmen standing guard
Crossfire to the marionettes, Slip into the edge of death...